John Yoo is a professor of law at the UC Berkeley School of Law. He has served on the faculty since 1993, with leaves of absence to work for Supreme Court Justice Clarence Thomas, the U.S. Senate Judiciary Committee and the Department of Justice under president George W. Bush. As deputy assistant attorney general in the Office of Legal Counsel in the wake of the 9/11 terrorist attacks, Yoo played a major role in defining the legality of certain methods of enhanced interrogation and torture. He also helped establish the constitutional powers of the president in wartime. He is the author of many books, including “Crisis and Command: The History of Executive Power From George Washington to George W. Bush” and most recently “Point of Attack: Preventive War, International Law and Global Welfare.”

Professor Yoo sat down with the Weekender last week to chat about the state of U.S. foreign affairs 13 years after 9/11, facing Jon Stewart on the Daily Show and his experiences teaching in Berkeley as a well-known conservative. Answers have been edited for clarity and length.

Daily Cal: Speaking about your new book at an American Enterprise Institute forum in April, you said, “If there is a norm against war, it should be one that countries can breach, if it makes the world better off after the war.” So, war — what is it good for?

John Yoo: There are things that are worse than war, and I think that’s why we fight them. The obvious example is stopping aggression by other countries. It would seem, certainly, that going to war against imperial Japan and Nazi Germany in the 1930s and ’40s was a good use of war. I think you could look at some of the humanitarian wars that the United States has conducted over the years. Using the armed forces to stop vast human rights disasters like Kosovo, perhaps.

The case that should really bother everyone is Rwanda, where we didn’t intervene, and a few thousand Western troops could have stopped the deaths of over a million Rwandans. I think also of what’s going on Syria right now. The estimates are at 175,000 civilians killed in Syria in the fighting.

DC: Did you have a sense while working in the Department of Justice, when 9/11 struck, that the attacks were going to not only redefine war and the way Americans understand it, but also have dramatic political impacts?

JY: I knew it would change the way Americans viewed war. Until 9/11, wars were quite conventional. Nations fighting each other, using conventional armed forces, operating on battlefields that were fairly defined. What 9/11 ushered in, at least for the American experience, was wars against groups that were not states, that would not fight out in the open field dressed in uniforms and operating conventional weapons in regular armed groups. War became a lot less about having more tanks, bigger warheads, more missiles, more airplanes than the other side.

(The war on terror) is different in that success is not really based on firepower — it’s based on intelligence and information. (It’s also) going on a lot longer. Americans are used to short wars. It’s been 13 years, and we’re still fighting terrorist groups originating from the Middle East and inspired by a certain extreme Islamic ideology.

DC: Once 9/11 struck, you became a pretty outspoken advocate for a strong presidency.

JY: Well, I was before 9/11, also. I wrote before and after 9/11 that the presidency’s primary function is to protect the United States’ national security and that in wartime, the presidency’s powers expand because the pressure on the country is higher.

The presidency was designed by the Framers to be the institution of government that would fight wars, because it could act quickly and swiftly. Our legislature has 535 people in it — it takes them a long time even to make up their minds. That’s the exact opposite body you would want to wage war. And the judiciary certainly can’t do it.

Certainly, the 9/11 attacks changed our politics by enhancing the power of the presidency and the defense department and the intelligence agencies. That’s definitely true.

DC: Does a strong presidency still give the United States its best chance to successfully address current international crises in Ukraine and Iraq?

JY: Oh yeah. How else could we do it? That’s something I will sometimes ask in debates — would you want Congress to actually run what we’re doing in Ukraine?

That’s not to say Congress is silent. Part of the argument I’ve made that people tend to overlook is that I think Congress has very powerful checks on the president, particularly through the power of purse. If Congress doesn’t choose to pay for any war and chooses not to pay for a create a certain kind of armed forces, then the president can’t fight a war. But in fact, Congress creates the kind of armed forces that are used offensively.

If you look at our military, it is designed to go to other people’s countries and fight wars there so that nothing ever gets here. So, in many ways, Congress and the president agree. They may fight over certain individual conflicts, but when it comes to the overall American strategy of waging war abroad, the president and Congress have agreed since WWII.

DC: One moment that you’re probably more remembered for among members of my generation is yourappearanceon The Daily Show with Jon Stewart in 2010. Stewart later described talking with you as something “like interviewing sand,” it was so hard.

JY: Do you feel like you’re interviewing sand right now?

DC: I don’t — but I think I have a slightly different objective than Stewart did.

JY: You know, he has this piece of paper in front of him. When you go on most interview shows, there’s a producer who writes up all these questions and (the host) asks them. (Stewart), to his credit, I think read my book — but then he had no written questions. He had this piece of paper in front of him that actually had nothing on it.

I’ve spent 20 years at Berkeley dealing with smart, unprepared people. And that’s how I treated him. People tend to think I did better than him, but that’s the way I am in class, too. I didn’t do anything especially different to prepare for going on his show. In fact, I didn’t prepare at all.

DC: The public’s memory of your time at the Justice Department under President Bush from 2001 to 2003 has focused on the so-called “Torture memos,” which defined torture as only those interrogation methods resulting in pain that rises “to the level of death, organ failure, or the permanent impairment of a significant body function.” You also worked on issues of separation of powers and electronic surveillance. What do you consider your most important work in the Bush administration?

JY: Obviously, it was how to respond to terrorism. The two issues were interrogation and electronic surveillance.

Under the Bush administration, our intelligence gathering was tough because of the circumstances forced on us by war — but it worked. You have an administration in power now that has pulled back and been quite severe on our intelligence agencies, and you’ve seen the results. The bill is coming due now.

DC: You’ve been teaching at UC Berkeley’s law school for more than 20 years now. Obviously your political orientation stands a bit against the prevailing political winds here. What initially attracted you here, and what’s kept you around?

JY: It’s one of the great universities in the world, and one of the great law schools in the world. I’ve always thought myself very fortunate to have gotten a position here.

I’ve always lived in liberal environments. The only time I’ve ever worked in a conservative environment was two years in the Bush administration, and I can’t say I enjoyed it all that much. I’m used to being surrounded by liberals. Liberals make better food, they have entertaining cultural activities, they’re good at making handmade items. It’s always good to live in liberal towns, I think. Conservatives are not having any fun in conservative towns.

DC: Did you know what to expect coming out here?

JY: No. I had no idea. Berkeley is famous throughout the country for being a liberal university with a lot of protests and activism, but it was the weirdness of it that I had no preparation for. It has great things — great food, interesting things going on — but also just complete disorder.

A lot of things that people in the rest of the country think are crazy about Berkeley are not about the university, they’re about the town. The town is crazy. The university is really no different than other top universities that I’ve seen and been to, but the town is really unique in its insanity. There’s no town like this in America — it’s really bizarre.

DC: You’ve faced more than a few instances of vocal opposition from students and faculty on campus over the years. In 2009, for example, UC Berkeley economics professor Brad DeLong wrote a letter to then-Chancellor Robert Birgeneau that not only condemned the “Torture memos,” but also accused you of being an intellectual “weathervane” that blows with the prevailing political winds.

JY: I find that very hard to understand. I don’t think he read anything I’ve written.

I’ve been very consistent in defending the president’s authority to use force without Congressional authorization. I’ve got an article out today defending President Obama’s right to attack ISIS in Syria and Iraq without having to go to Congress for permission. I defended President Bush’s right, of course, in office. And I also defended President Clinton’s right to use air power in Kosovo. I just have to attribute it to people like him reading blogs on the Internet, rather than sitting down and reading (my) actual written products.

On the other hand, it’s a free university — anyone’s allowed to pop off and say whatever they want about anything. That’s part of why Berkeley is such a lively place and also a bit of a nutty place. If an economics professor wants to try to issue positions on Constitutional law, I don’t know why not.

I could say Keynesians have ruined our economy for the last six years — look at all the millions of jobs that we’ve lost and the disaster Obamacare is. But just because he or some other economist might be in favor of that, I wouldn’t say they should be kicked off the faculty because their policy choices have led to millions of Americans losing their jobs and staying out of work. That’s their right to say that, if they want.

That’s the one thing about some people at Berkeley. Not the university or the administration, but there are always some people around who can’t tolerate diversity of viewpoint. But, I have to say, unlike some conservatives who like to pick on Berkeley for this reason, I don’t think Berkeley is actually different than most other universities. I actually think there are several top universities that are worse when it comes to promoting ideological diversity.

You asked me earlier about (living and working in) conservative and liberal environments. It was good for me to go to universities that were liberal, because it really challenged me to think through why I thought certain things. So I hope that people here at the university realize that, if there are a lot of liberal students, it would be good for them to have to confront conservative ideas.